Polyvinyl acetal resin and film therefrom



Patented Nov. 9, 1943 POLYVINYL ACETAL RESIN AND mm THEREFRONE' William 0. Kenyon and Wendell H. McDowell, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 13, 1940,

Serial No. 340,368

6 Claims.

This invention relates to resins and more particularly to polyvinyl acetyl resins, and to film made of such resins.

A number of polyvinyl acetal resins are known. These known resins are characterized by containing, attached to the polyvinyl chain, acetal groups and hydroxyl groups. Sometimes, the resins also contain ester groups attached to the polyvinyl chain.

Polyvinyl resins can be prepared by condensing a polyvinyl alcohol withone or more aldehydes, inthe presence of an acetal condensation catalyst. Prepared in this way, polyvinyl acetal resins always contain acetal groups and hydroxyl groups. Polyvinyl acetalresins can also be prepared by deesterifying a polyvinyl ester and con-' comitantly condensing one or more aldehydes with the deesterified product, or similarly, polyvinyl acetal resins can be prepared by partially deesteriiying a polyvinyl ester and subsequently condensing oneor more aldehydes with the deesterifled product. Prepared in either of the latter two ways, the polyvinyl acetalresins contain acetal, hydroxyl and ester groups.

Among the known polyvinyl acetal resins, the polyvinyl acetaldehyde acetal resins (containing an acetate group content equivalent to not more than about five percent by weight of polyvinyl acetate) have appeared to be the most interesting of the polyvinyl acetal resins in which the acetal linkages are formed from but a single "aldehyde. These polyvinyl acetaldehyde acetal resins appeared to be useful for a variety of purposes in the plastics field. For example, such resins can be cast from ordinaryvsim'ple solutions into the form of film or sheet. However, the film or sheet is too brittle to be adapted commercially to certain uses; for instance, the film or sheet is too f brittle to serve as a support for light-sensitive photographic coatings in the manufacture of cinematographic film. Efforts to decrease the brittleness .Ofsuch resins by changingthe chemical composition thereof, viz. by increasing the hy-' droxyl group content, have resultedin resins which are too water-susceptible to be employed commercially in the manufacture of cinematoraphic film.

replaced by propionate or butyrate groups, a resin is obtained fromwhich film or sheet of very good flexibility and low water susceptibility can be made.

It is, accordingly, an object of our invention to provide new resins. A further object is to provide a process for preparing such resins. A still further object is to'provide film or sheet of such resins. Other objects will become apparent hereinafter.

, According to a preferred embodiment of our invention, we substantially completely replace the hydroxyl groups of polyvinyl acetal resins by esterifying the hydroxyl groups with anhydrides of monobasic carboxylic acids, in the presence of a sufficient quantity of pyridine to dissolve the starting polyvinyl acetal resin; Heat accelerates the esterification. The following examples will serve to illustrate the manner of preparing our new resins. These examples are not intended to limit our invention.

Example 1 100 g. of a'polyvinyl acetaldehyde acetal resin (containing a hydroxyl group content equivalent to about 6.5% by weight of polyvinyl alcohol and an acetate group content equivalent to about 3.3% by weight of polyvinyl acetate) were dissolved in 1000 cc. of pyridine. 500 cc. of propionic anhydride were added to the resulting solution and the mixture was heated, under reflux, at

The mixture was C, for about 2 /2 hours. cooled, and diluted with 1000 cc. of acetone. The diluted solution was poured into water to precipitate the resin. The precipitated resin was dissolved in acetone and reprecipitated in water.

The resin was then allowed to dry in the air. An analysis showed the resin to contain an acetate group content equivalent toabout 3.1 by weight of polyvinyl acetate, a propionate group content equivalent to about 13.7% by weight of polyvinyl propionate and substantially no hydroxyl group content.

Examplez 100 g. of the same kind of polyvinyl acetaldehyde acetal resin which was employed in Ex- ,ample l were dissolved in 1000 cc. of pyridine.

500 cc. of butyric anhyride were added to the resulting solution and the mixture was heated, undei: reflux, at 100. C. for about 2 hours. The mixture was then diluted with 100 cc. oi acetone.

The diluted solutionwas poured into water to precipitate the resin. The precipitated resin was dissolved in acetone and reprecipitated in water. The resin was then allowed to dry in the air.

propionaldehyde acetal resins, polyvinyl chloroacetaldehyde aceta1 resins, polyvinyl acetaldehyde-benzaldehyde acetal resins and polyvinyl benzaldehyde acetal resins can be substantially completely replaced by ester groups to give resins of improved flexibility and lower watersuscep tibility.

To prepare film or sheet from our new resins, we first dissolve about 1 part of the resin in from 2% to 4 /2 parts of a suitable solvent, such as acetone or a mixture of 90% (by volume) of acetone and methyl alcohol or ethylene dichloride for example. If necessary to obtain a: clear solution, larger quantities of solvent may be employed. Such a solution-is then cast onto a fllmforming surface, suchas a metal or glass plate, or a revolving drum, to desired thickness and the resulting film or sheet is allowed to dry. Drying may be facilitated by blowing warm air over the drying film or sheet.- When sufliciently dry, the fllm or sheet is stripped from the filmforming surface and cured by treating with content.

Flexibility ceptibi ity (number of Resin Hydroxyi (swell and folds before shrink amplibreak) tude) Polyvinyl acetaldehyde acetal 21 23 Propionateri polyvinyl acetaldehyde acetaL. 13

From the foregoing comparative data, it is apparent that our new resins have a lower moisas a laminating material, e. g. between sheets of glass, particularly if suitably plasticized. Our

1. A process for preparing a polyvinyl acetaldehyde acetal resin substantiallyfree from hydroxyl groups comprising substantially completely esterifylng with ester groups selected from the group consisting of propionate and butyrate groups the hydroxyl groups in a polyvinyl acetaldehydelacetal resin containing no acetal groups other than acetaldehyde acetal groups, a hydroxyl group content equivalent to about 6.5 per cent by weight of polyvinyl alcohol and an acetate group content equivalent to about 3.3 per cent by weight of polyvinyl acetate.

2. A process for preparing" a polyvinyl acetaldehyde acetal resin substantially free from hydroxyl groups comprising substantially completely esterifying with propionategroups the hydroxyl groups in a polyvinyl acetaldehyde acetal resin containing no acetal groups other than acetaldehyde acetal groups, a hydroxyl group content equivalent to about 6.5 per cent. by weight ofpolyvinyl alcoholand an acetate group content equivalent to about 3.3 per cent by weight of polyvinyl acetate.

containing no acetal groups other than acetaldehyde acetal groups, a hydroxyl group content equivalent to about 6.5 per cent by weight of polyvinyl alcohol and an acetate group content equivalent to about,3.3 .per cent by weight of ture susceptibility and a greater flexibility than. [I

the resins containing an appreciable hydroxyl group content.

Our new resins can be pressed into blocks and skived to thin sheets or layers which can be used polyvinyl acetate.

4. The polyvinyl acetal resin obtainedby the process of claim 1. I y

I 5. The polyvinyl acetal resin obtained by the process of claim-2.

6. The polyvinyl acetal resin obtained by. the process of claim 3.

WILLIAM O. KENYON. 

